Systems and methods for integrated wave power charging for ocean vehicles

ABSTRACT

A system includes an unmanned underwater vehicle (UUV), a reaction structure configured to deploy from a body of the UUV, and one or more tendons connecting the reaction structure to the body of the UUV, wherein the reaction structure deploys at a depth below the body of the UUV. The system further includes one or more power take-out (PTO) units coupled to or between the reaction structure and the UUV. The system further includes a control unit coupled to the one or more PTO units to convert energy from waves on a surface of a body of water for use in other systems within the UUV.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims the benefit of U.S. Provisional Application No.63/023,517, filed on May 12, 2020, which is incorporated by referenceherein in its entirety.

STATEMENT OF FEDERALLY SPONSORED RESEARCH

This invention was made with Government support under DOE DE-SC0020864.The Government has certain rights to this invention.

BACKGROUND

This disclosure relates generally to wave energy systems. Morespecifically, this disclosure relates to harnessing wave energy to powerwater vehicles such as unmanned underwater vehicles.

SUMMARY

The subject matter of the present application has been developed inresponse to the present state of the art, and in particular, in responseto the problems and disadvantages associated with conventionaldeposition that have not yet been fully solved by currently availabletechniques. Accordingly, the subject matter of the present applicationhas been developed to provide embodiments of a system, an apparatus, anda method that overcome at least some of the shortcomings of prior arttechniques.

Disclosed herein is a system. The system includes an unmanned underwatervehicle (UUV), a reaction structure configured to deploy from a body ofthe UUV, and one or more tendons connecting the reaction structure tothe body of the UUV, wherein the reaction structure deploys at a depthbelow the body of the UUV. The system further includes one or more powertake-out (PTO) units coupled to or between the reaction structure andthe UUV. The system further includes a control unit coupled to the oneor more PTO units to convert energy from waves on a surface of a body ofwater for use in other systems within the UUV. The preceding subjectmatter of this paragraph characterizes example 1 of the presentdisclosure.

The control unit is further configured to store the electrical energy.The preceding subject matter of this paragraph characterizes example 2of the present disclosure, wherein example 2 also includes the subjectmatter according to example 1, above.

The one or more PTO units is coupled to the reaction structure. Thepreceding subject matter of this paragraph characterizes example 3 ofthe present disclosure, wherein example 3 also includes the subjectmatter according to any one of examples 1-2, above.

The one or more PTO units is coupled to the UUV. The preceding subjectmatter of this paragraph characterizes example 4 of the presentdisclosure, wherein example 4 also includes the subject matter accordingto any one of examples 1-3, above.

The one or more PTO units is coupled between the reaction structure andthe UUV. The preceding subject matter of this paragraph characterizesexample 5 of the present disclosure, wherein example 5 also includes thesubject matter according to any one of examples 1-4, above.

The reaction structure is configured to move from an undeployed positionto a deployed position. The preceding subject matter of this paragraphcharacterizes example 6 of the present disclosure, wherein example 6also includes the subject matter according to any one of examples 1-5,above.

The undeployed position comprises that the reaction structure isdirectly coupled to the body of the UUV. The preceding subject matter ofthis paragraph characterizes example 7 of the present disclosure,wherein example 7 also includes the subject matter according to any oneof examples 1-6, above.

The deployed position comprises that the reaction structure is onlycoupled to the body of the UUV via the one or more tendons. Thepreceding subject matter of this paragraph characterizes example 8 ofthe present disclosure, wherein example 8 also includes the subjectmatter according to any one of examples 1-7, above.

The UUV is an autonomous underwater vehicle (AUV). The preceding subjectmatter of this paragraph characterizes example 9 of the presentdisclosure, wherein example 9 also includes the subject matter accordingto any one of examples 1-8, above.

The one or more tendons have rigid connections to the body of the UUV.The preceding subject matter of this paragraph characterizes example 10of the present disclosure, wherein example 10 also includes the subjectmatter according to any one of examples 1-9, above.

Disclosed herein is a system. The system includes an unmanned underwatervehicle (UUV), a flotation structure configured to deploy from a body ofthe UUV, and one or more tendons connecting the flotation structure tothe body of the UUV, wherein the flotation structure deploys above thebody of the UUV. The system further includes one or more power take-out(PTO) units coupled to or between the flotation structure and the UUV.The system further includes a control unit coupled to the one or morePTO units to convert energy from waves on a surface of a body of waterfor use in other systems within the UUV. The preceding subject matter ofthis paragraph characterizes example 11 of the present disclosure.

The control unit is further configured to store the electrical energy.The preceding subject matter of this paragraph characterizes example 12of the present disclosure, wherein example 12 also includes the subjectmatter according to example 11, above.

The one or more PTO units is coupled to the flotation structure. Thepreceding subject matter of this paragraph characterizes example 13 ofthe present disclosure, wherein example 13 also includes the subjectmatter according to any one of examples 11-12, above.

The one or more PTO units is coupled to the UUV. The preceding subjectmatter of this paragraph characterizes example 14 of the presentdisclosure, wherein example 14 also includes the subject matteraccording to any one of examples 11-13, above.

The one or more PTO units is coupled between the flotation structure andthe UUV. The preceding subject matter of this paragraph characterizesexample 15 of the present disclosure, wherein example 15 also includesthe subject matter according to any one of examples 11-14, above.

The flotation structure is configured to move from an undeployedposition to a deployed position. The preceding subject matter of thisparagraph characterizes example 16 of the present disclosure, whereinexample 16 also includes the subject matter according to any one ofexamples 11-15, above.

The undeployed position comprises that the flotation structure isdirectly coupled to the body of the UUV. The preceding subject matter ofthis paragraph characterizes example 17 of the present disclosure,wherein example 17 also includes the subject matter according to any oneof examples 11-16, above.

The deployed position comprises that the flotation structure is onlycoupled to the body of the UUV via the one or more tendons. Thepreceding subject matter of this paragraph characterizes example 18 ofthe present disclosure, wherein example 18 also includes the subjectmatter according to any one of examples 11-17, above.

The UUV is an autonomous underwater vehicle (AUV). The preceding subjectmatter of this paragraph characterizes example 19 of the presentdisclosure, wherein example 19 also includes the subject matteraccording to any one of examples 11-18, above.

The one or more tendons have rigid connections to the body of the UUV.The preceding subject matter of this paragraph characterizes example 20of the present disclosure, wherein example 20 also includes the subjectmatter according to any one of examples 11-19, above.

Other aspects and advantages of embodiments of the present inventionwill become apparent from the following detailed description, taken inconjunction with the accompanying drawings, illustrated by way ofexample of the principles of the invention.

BRIEF DESCRIPTION OF THE DRAWINGS

In order that the advantages of the subject matter may be more readilyunderstood, a more particular description of the subject matter brieflydescribed above will be rendered by reference to specific embodimentsthat are illustrated in the appended drawings. Understanding that thesedrawings depict only typical embodiments of the subject matter and arenot therefore to be considered to be limiting of its scope, the subjectmatter will be described and explained with additional specificity anddetail through the use of the drawings, in which:

FIG. 1 depicts an unmanned underwater vehicle (UUV), according to one ormore embodiments of the present disclosure;

FIG. 2 depicts an unmanned underwater vehicle (UUV) with a reactionstructure beginning to deploy, according to one or more embodiments ofthe present disclosure;

FIG. 3 depicts an unmanned underwater vehicle (UUV) with a reactionstructure deployed, according to one or more embodiments of the presentdisclosure;

FIG. 4 depicts an unmanned underwater vehicle (UUV) with an internal airbag on the UUV, according to one or more embodiments of the presentdisclosure;

FIG. 5A depicts an unmanned underwater vehicle (UUV) with an externalair bag on the UUV, according to one or more embodiments of the presentdisclosure;

FIG. 5B depicts an unmanned underwater vehicle (UUV) with two externalair bags on the UUV, according to one or more embodiments of the presentdisclosure;

FIG. 6 depicts a float and reaction structure, according to one or moreembodiments of the present disclosure;

FIG. 7 depicts a graph of bow tendon tension (kN) as a function of time,according to one or more embodiments of the present disclosure;

FIG. 8 depicts an isometric view a power take-out unit (PTO), accordingto one or more embodiments of the present disclosure;

FIG. 9 depicts an exploded view of a power take-out unit (PTO_,according to one or more embodiments of the present disclosure.

Throughout the description, similar reference numbers may be used toidentify similar elements.

DETAILED DESCRIPTION

It will be readily understood that the components of the embodiments asgenerally described herein and illustrated in the appended figures couldbe arranged and designed in a wide variety of different configurations.Thus, the following more detailed description of various embodiments, asrepresented in the figures, is not intended to limit the scope of thepresent disclosure, but is merely representative of various embodiments.While the various aspects of the embodiments are presented in drawings,the drawings are not necessarily drawn to scale unless specificallyindicated.

The present invention may be embodied in other specific forms withoutdeparting from its spirit or essential characteristics. The describedembodiments are to be considered in all respects only as illustrativeand not restrictive. The scope of the invention is, therefore, indicatedby the appended claims rather than by this detailed description. Allchanges which come within the meaning and range of equivalency of theclaims are to be embraced within their scope.

Reference throughout this specification to features, advantages, orsimilar language does not imply that all of the features and advantagesthat may be realized with the present invention should be or are in anysingle embodiment of the invention. Rather, language referring to thefeatures and advantages is understood to mean that a specific feature,advantage, or characteristic described in connection with an embodimentis included in at least one embodiment of the present invention. Thus,discussions of the features and advantages, and similar language,throughout this specification may, but do not necessarily, refer to thesame embodiment.

Furthermore, the described features, advantages, and characteristics ofthe invention may be combined in any suitable manner in one or moreembodiments. One skilled in the relevant art will recognize, in light ofthe description herein, that the invention can be practiced without oneor more of the specific features or advantages of a particularembodiment. In other instances, additional features and advantages maybe recognized in certain embodiments that may not be present in allembodiments of the invention.

Reference throughout this specification to “one embodiment,” “anembodiment,” or similar language means that a particular feature,structure, or characteristic described in connection with the indicatedembodiment is included in at least one embodiment of the presentinvention. Thus, the phrases “in one embodiment,” “in an embodiment,”and similar language throughout this specification may, but do notnecessarily, all refer to the same embodiment.

Furthermore, the described features, advantages, and characteristics ofthe invention may be combined in any suitable manner in one or moreembodiments. One skilled in the relevant art will recognize, in light ofthe description herein, that the invention can be practiced without oneor more of the specific features or advantages of a particularembodiment. In other instances, additional features and advantages maybe recognized in certain embodiments that may not be present in allembodiments of the invention.

Reference throughout this specification to “one embodiment,” “anembodiment,” or similar language means that a particular feature,structure, or characteristic described in connection with the indicatedembodiment is included in at least one embodiment of the presentinvention. Thus, the phrases “in one embodiment,” “in an embodiment,”and similar language throughout this specification may, but do notnecessarily, all refer to the same embodiment.

There are a variety of ocean-based systems that can benefit fromincorporation of built-in energy harvesting solutions to extend orexpand at least one of the following, among others: performancecapabilities, lifetime, range, communication capability, and/or remoteoperation/control capability. These include, but are not limited tofloating or submerged buoys, floating or sub-surface platforms thatsupport various types of equipment, surface or under-water vehicles,including unmanned underwater vehicles (UUVs). While the descriptionbelow focuses on UUVs, it should be understood the embodiments of theinventions described below may be incorporated into any one of thesystems described in the previous sentence, or any other ocean-basedsystem.

UUVs, which include autonomous underwater vehicles (AUVs) and RemoteOperated underwater Vehicles (ROVs), are gaining increasing acceptanceand starting to be applied to several uses. Adoption of UUV technologyhas recently experienced rapid growth, fueled by possibilities opened upthrough technology advances and growing awareness of these capabilitiesby users and customers. Coupled with advances in modern robotics, UUVsare performing maritime tasks in days that used to take fleets of shipsmonths to complete. UUVs are particularly useful as unmanned surveyplatforms, and typically have an array of on-board sensors to collectdata for a variety of applications. They are used widely for a varietyof commercial applications including persistent ocean remote conditionmonitoring, marine search and rescue, marine wildlife monitoring,underwater construction, aquaculture, surveillance, and inspections ofsubsea infrastructure. In addition, there are a number of criticalmilitary operations that are increasingly reliant on UUVs including minecountermeasures, surveillance, submarine detection, etc. In bothcommercial and military arenas, UUVs offer the potential to be cheaper,less complex, safer and more reliable than human-powered vehicles. TheUS Navy, in particular, is starting to restructure its operationssignificantly to take advantage of the resilience, surveillance, costsavings, and stealth benefits of operating many small UUVs, as comparedto large ships.

Although UUVs are seeing increasing adoption, they have not yet reachedtheir full potential. While ROVs draw power from an umbilical connectionand are remotely operated from a surface vessel, AUVs are autonomous anduntethered systems and require a power source to be carried onboard.Available power is therefore a key constraint for most AUVs. The powerdraw from various sensors that may be carried on an AUV is indicated inTable 1 and it is clear that an increase in available power by even asmall amount can be game-changing for AUV applications. It has beenshown that should greater power be available on board AUVs the mostdesired increase in functionality is longer mission durations, highersampling rate, more sensing capability and improved communicationcapability.

Generally, an on-board battery is used for all power demands, includingpropulsion, communication, sensors, and data acquisition. Lithiumbatteries are the most common type of battery used in AUVs, and they canallow operation for a number of hours, with the mission duration greatlyinfluenced by the vehicle speed or data collection rate. An AUV istypically built around a given battery capacity which can occupy up to75% of the interior of the AUV. Extended duration missions require theAUV to be recovered and batteries to be recharged or swapped, generallyrequiring the intervention of a support vessel. Reducing the number ofrecoveries & redeployments for a given mission duration is an obviousdriver to reduce costs and increase safety.

TABLE 1 Typical sensor power requirements for AUVs, according toTownsend, N. C. (2016). IET Renewable Power Generation, 10(8),1078-1086. Sensor Power [W] Pressure Sensor 0.1 (typ) [22] Digitalcompass 0.132 (typ) 0.014 (sleep) [9] Sound Velocity sensor 0.25 (typ)[29] Echo Sounder 0.25 (max) [12] Fluorometer 0.3 (typ) [8] Precisiontiming reference 0.3 (max) [14] Hydrophone 0.12 to 0.3 (typ) [26] MEMSAHRS and GPS/INS 0.675 to 0.95 (typ) [31] Turbulence Sensor 1 (typ) [19]2D imaging sonar 3 (typ) [2] Conductivity Temperature Depth (CTD) Sensor3.42 (incl. pump) [23] Digital Camera 5 (typ) [11] Sidescan sonar 5 (typexclude CPU) [24] LBL Acoustic Positioning System 2.5 to 5.5 (transmit),1.3 (max receive) 0.005 to 0.285 (listen mode) 0.0025 (standby) [16]Nitrate Sensor 7.5 (max) [27] Doppler velocity log 12 (max transmit) 2(average transmit) 1.1 (typ) [10] 3D imaging sonar 15 (typ) [18]Underwater RF 16 (transmit) 5 (receive) 0.005 (sleep) [30] CurrentProfiler 20 to 0.3 (Transmit) 0.2 to 1.4 (typ) [3] Side scan soner andSub bottom profiler 30 (max) [1] Navigation and control system 50 (max)2 (active listening) 0.7 (sleep) [7] Multibeam Swath Bathymetry andSidescan 50 (max) 20 (standby) [13] Transponder 50 (max) 2 (active) 0.7(sleep) [6] Underwater laser scanner 144 (typ) [28] AcousticCommunications 300 (transmit) 1.8 (receive/standby) 0.08 (standby) [15]

The approach we describe to mitigate this problem is to incorporate someself-recharging capability within the AUV. This allows the AUV toextract energy from its surrounding environment and eliminates the needto recover the vehicle for recharging until the mission is complete,thereby allowing a significant increase to the physical range ofoperation. Furthermore, this can result in an increased availability ofpower for internal systems which can allow greater capabilities to beincorporated or utilized within the AUV. A number of approaches havebeen attempted to incorporate on-board energy harvesting on AUVs withlimited success.

Wave energy could be an attractive solution for AUV powering. Waveenergy has a high energy density, is available anywhere in the ocean,can potentially be harnessed without rising above the ocean surface, andis available 24 hours a day. Wave generated propulsion is demonstratedon commercially available systems, e.g., waveglider. However, theefforts on electricity generation for AUV's from wave energy to datehave focused on rocking or gyroscopic systems and resulted in less than1 Watt of average power, an order of magnitude less power than thedescribed approach.

By including a wave powered recharging capability this will allow theAUV to operate for significantly longer periods of time, potentiallyindefinitely. This reduces the cost per mission, allows additionalsensors and communications, enables more complex missions, and mostimportantly, will allow substantially more ocean science to becompleted. The approach described is scalable and adaptable and canpotentially be applied to any AUV. This approach is described for atorpedo shaped AUV as this is the dominant form of AUV in use, howeverthe described principle is applicable to any arbitrary shaped AUV.

Under nominal operations the AUV would operate normally and with anidentical external profile. When the AUV desires to recharge, the AUVbody will reconfigure into a two-body, wave energy converter through thelowering of a reaction structure. While the reaction structure may beinternal to, external to, or part of the body of the AUV, in oneembodiment, the reaction structure may be part of or align with theexterior casing of the AUV.

Referring now to FIG. 1, an unmanned underwater vehicle (UUV) as part ofa system 200 is shown. Although the system 200 is shown and describedwith certain components and functionality in the following paragraphs,other embodiments of the system 200 may include fewer or more componentsto implement less or more functionality. The system 200 includes anunmanned underwater vehicle (UUV). In some embodiments, the UUV may bean AUV or a ROV. In the illustrated embodiment, the UUV includes apropeller to allow the UUV to maneuver through the water. The UUV mayinclude other systems that require power to function including, but notlimited to, sensors, propulsion systems, communication systems, dataacquisition systems.

The system 200 also includes a reaction structure 204 configured todeploy from a body 202 of the UUV. In the illustrated embodiment, thereaction structure 204 aligns with an exterior casing of the UUV. Thedeployable reaction structure 204 allows the UUV to maneuver and performfunctions either in a deployed or undeployed position. As shown, thereaction structure 204 aligns with the body 202 of the UUV forstreamlined movement.

The system 200 also includes one or more tendons (not shown in FIG. 1).The one or more tendons connect the reaction structure 204 to the body202 of the UUV. The reaction structure 204 may be configured to deployat a depth below the body 202 of the UUV. In other embodiments, thereaction structure 204 may be configured to deploy above the body 202 ofthe UUV.

The system 200 further includes one or more power take-out (PTO) units(internal to the UUV). See FIGS. 8 and 9 for an example of a PTO unit.The PTO unit(s) may be coupled to the reaction structure 204, to the UUVor the body 202 of the UUV, or coupled between the reaction structure204 and the UUV.

The system further includes a control unit or a plurality of controlunits in some embodiments. The control unit (or controller) may includehardware or software that is capable of controlling the various featuresof the system 200 and performing functions of the system 200 as needed.In some embodiments, the control unit is coupled to the one or more PTOunits. The control unit may be configured to harness and convert energyfrom the waves on a surface of a body of water. The relative positioningof the body 202 of the UUV and the reaction structure 204 connected bythe tendons 206 (not shown in FIG. 1, see FIG. 3), and movement causedby the waves on the UUV allow for tensile forces (and other forces) tobe harnessed from a PTO unit. The control unit may be configured toconvert the wave energy for use in the other systems within the UUV.

Referring now to FIG. 2, the reaction structure 204 is beginning to bedeployed and lowered from the body 202 of the UUV. As depicted, thereaction structure 204 is being deployed below the body 202 but can bedeployed in other directions in other embodiments.

Referring now to FIG. 3, the reaction structure 204 is in a deployedposition below the body 202 of the UUV. As shown, the system 200 canmove back and forth between a deployed position (shown in FIG. 3) and anundeployed position (shown in FIG. 1) as needed. When recharging isneeded, the UUV may deploy the reaction structure 204 and harness energyto recharge the UUV systems without requiring the UUV to return to base.

As depicted, the reaction structure 204 is coupled to the body 202 ofthe UUV by a pair of tendons 206. Also depicted are extension springs208 which may be utilized to better harness the energy but are notnecessary in many embodiments.

In some embodiments, the reaction plate 204 can be altered (afterlowering) to a different shape that may provide additional benefits froma performance standpoint. In such embodiments, additional means may beincluded in the reaction structure to facilitate realignment, expansion,etc. so as to facilitate the reaction structure 204 to be altered from abaseline shape to form a more hydrodynamically desirable shape. In someembodiments of the invention, this shape may be one that provides anincreased effective drag coefficient in the upward direction relative tothe downward direction. In some embodiments of the invention, thealtered shape may provide increased added mass relative to the baselineshape.

In some embodiments, the UUV body 202 will act as a float and will beconnected to the deployable reaction structure below it, and use thewave generated relative movement of these two bodies to generate power.Wave particle motion reduces by the square of the depth and thereforethe wave loads on the UUV body 202 will be substantially greater thanthose on the reaction structure, deployed a few meters below.Accordingly, the UUV will generate the most power when the float is atthe surface of a body of water, however this is not a requirement foroperation and by positioning the UUV some distance below the surface,but still in the presence of waves. The UUV can still generate power ifpositioned below the surface.

In very large ocean waves where there is a risk of damage at thesurface, the AUV can enter the recharging configuration at some depthbelow the surface, where the energy is reduced. The production of powerfrom the relative motion the reaction plate and AUV body is similar to atwo-body wave energy converter and will be described below. Whilecharging, the AUV would be able to use its already existing systems,such as propulsion, buoyancy engine and navigation to autonomouslymaintain target charging depth, maintain heading and charge onboardbatteries.

In some embodiments, a surface float (or flotation structure), separatefrom the UUV body may be deployed from the UUV such that it is thissurface float that reacts against the reaction structure. Thisconfiguration may have the advantage that the surface float can have ashape suitable for optimal energy capture from the waves. In suchembodiments, the UUV may or may not form or function as the reactionstructure 204.

In the case where the UUV forms the reaction structure, the system maybe capable of additional shape alterations that may allow it to functionsuitably as a reaction structure. In some embodiments, the PTO may be onthe UUV body that forms the reaction structure.

In such embodiments, the system includes an unmanned underwater vehicle(UUV), a flotation structure configured to deploy from a body of theUUV, and one or more tendons connecting the flotation structure to thebody of the UUV, wherein the flotation structure deploys above the bodyof the UUV. The system further includes one or more power take-out (PTO)units coupled to or between the flotation structure and the UUV. Thesystem further includes a control unit coupled to the one or more PTOunits to convert energy from waves on a surface of a body of water foruse in other systems within the UUV.

If the UUV does not have a buoyancy engine, as may be the case with somesmall units, means may be included to facilitate additional buoyancy.This may include a mechanism to expand the structure either mechanicallyand/or through the use of an airtight elastic membrane within (or on)the upper surface of the AUV can be inflated (through a CO2 cartridge orsimilar).

Referring now to FIG. 4, an unmanned underwater vehicle (UUV) with aninternal air bag 212 on the body 202 of the UUV is shown. Referring toFIG. 5A, an unmanned underwater vehicle (UUV) with an external air bag212 on the body 202 of the UUV is shown. Referring to FIG. 5B, anunmanned underwater vehicle (UUV) with two external air bags 212 on thebody 202 of the UUV is shown.

In one embodiment, the air bag 212 could be on the exterior of the UUV(see FIGS. 5A and 5B). In another embodiment, the air bag 212 would beon the inside and the outer UUV casing would hinge open as it isinflated (see FIG. 4). In the latter case, the UUV body 202 can avoidany additional drag during operation when the airbag is deflated.However, in the case of there being no buoyancy engine, the powerlimiting functionality described above would not be available.

In some embodiments of the invention, controls and body mechanics may beincluded to alter the physical shape of the UUV body 202 itself so thatit can react more to the waves and capture a greater amount of energyfrom waves. In some embodiments, the water plane area of the structuremay be increased by opening up one or more additional structuresincluding, but not limited to fins, shields etc.

The reaction structure 204 and the UUV body 202 may be connected in manyways, including with tendons 206 or with rigid connections. Oneembodiment that utilizes one or more tendons is described below. Whendeployed, the recharging configuration would include either a singletendon 206 from the center of the UUV body 202 connected to the reactionstructure 204, or alternatively, two tendons 206, located axially alongthe body 202 of the UUV connected to the reaction structure 204. Thetwo-tendon configuration allows for both pitch and heave motion to beprimary contributors to relative (power generating) motion. Additionalmotion in surge, sway and yaw will also result in some secondary powergeneration. Other embodiments may include more than two tendons 206.

In some embodiments, the reaction structure 204 will be stowed againstthe body 202 of the UUV when not in use and then lowered below the UUVbody 202 to generate power. This naturally gives the reaction structure204 a hemispherical or partial hemispherical shape when deployed.Similar shapes have been shown to provide greatly increased added masscompared to flat plates. Increasing the added mass of the reactionstructure 204 greatly increases its performance.

In some embodiments, an UUV buoyancy engine can be used to control theoverall submergence of the system while generating power in order tomanage power and loads in larger sea states. It should be noted thatthis approach is a fail-safe approach, whereby if the tendon(s) were tofail, the AUV would remain on the surface and recoverable.

Referring to FIG. 6, a float 102 and reaction structure 104 is depictedwith three tendons 106 coupling them together. Such an apparatus iscapable of harnessing tension as described herein. Referring to FIG. 7,a graph of a Bow Tendon Tension (kN) is shown for both a floating system222 and for a submerged system 224 to show the difference.

The light weight of the reaction structure 204 relative to its areameans that drag forces may become large relative to inertial forces andcould mean that there will be a tendency for the tendons to experiencesnap loading. This can result in a risk of additional fatigue to thetendons 206. This can be mitigated in some embodiments by using variablegeometry, such that the reaction structure 204 will fold inward on thedownward travel, significantly reducing the drag area. This may beimportant in longer, larger waves where reaction forces are increasinglyrelated to the reaction structure velocities. In smaller, shorter waves,reaction forces may be dominated by inertial forces, and in these casesthe added mass terms may be relatively important.

In some embodiments, the UUV will have a somewhat limited buoyantrestoring force when acting as a float, and especially when submerged,which will limit the power production. This can be improved byincreasing the drag and added mass of the UUV body in heave by addinglongitudinal features (fins) in the horizontal plane that will notimpede normal streamwise flow when operating. This is not a requirementfor the invention to function but can be used to improve the powerperformance.

As noted, the relative motion of the two bodies creates a useable forceand displacement. This is converted into electrical energy through acompact power take-out (PTO). The choice of PTO in no way limits thescope of this invention and it is understood that the invention may beviable with many different types of PTO units. In some embodiments, thedesign of the PTO unit should be able to handle a long relativedisplacement between bodies to generate optimum power.

Referring now to FIG. 8, a PTO unit is shown. In the illustratedembodiment, a rotary approach is shown. The tendon 206 is connected tothe reaction structure (not shown) at its lower end, while the upper endpasses through a fairlead 312 and wraps around a small drum 310. Thefairlead 312 is used to channel the line onto the drum 310 and preventdamage to the tendon 206. In the presence of waves, the UUV float andreaction structure will oscillate relative to each other around theequilibrium point of the spring 208. This motion will therefore causethe drum 310 and the generator to rotate. The drum 310 is connected to adriveshaft 308 that is coupled to the generator (including a generatorrotor 306, generator stator 304) and supported by bearings 302. The PTOunit 300 includes a support structure 314 on which the bearings 302support the unit and the fairlead 312 fits into an opening 316 thatcouples the spring to the PTO unit 300. The other end of the spring 208is coupled to a point on the tendon 206.

FIG. 9 depicts an exploded view of the PTO unit 300 to better illustratethe various parts.

The described approach herein is scalable to both small and large UUVsand the power produced will scale roughly with Froude scaling (γ^(3,5)).In one example, a small UUV with around 9 kg displacement could producearound 5 W, while an UUV that is twice as large (such as a REMUS 100)may produce >10 times more power (over 50 W) and one that is 4 times aslarge (such as a Bluefin 21) may produce over 128 times more power (i.e.over 0.5 kW). The physical size of the device and the power produced bythe device can vary significantly, and embodiments of this invention canscale the range from very small amounts of power produced (e.g.micro-Watts), to very large amounts of power (e.g. many Kilo-Watts).

Methods of deploying a reaction structure 204 from a UUV are alsocontemplated herein.

Embodiments of components of the systems described herein might becoupled directly or indirectly to memory elements through a system bussuch as a data, address, and/or control bus. The memory elements caninclude local memory employed during actual execution of the programcode, bulk storage, and cache memories which provide temporary storageof at least some program code in order to reduce the number of timescode must be retrieved from bulk storage during execution.

It should also be noted that at least some of the operations for themethods may be implemented using software instructions stored on acomputer useable storage medium for execution by a computer. As anexample, an embodiment of a computer program product includes a computeruseable storage medium to store a computer readable program that, whenexecuted on a computer, causes the computer to perform operations,including an operation to monitor a pointer movement in a web page. Theweb page displays one or more content feeds. In one embodiment,operations to report the pointer movement in response to the pointermovement comprising an interaction gesture are included in the computerprogram product. In a further embodiment, operations are included in thecomputer program product for tabulating a quantity of one or more typesof interaction with one or more content feeds displayed by the web page.

Although the operations of the method(s) herein are shown and describedin a particular order, the order of the operations of each method may bealtered so that certain operations may be performed in an inverse orderor so that certain operations may be performed, at least in part,concurrently with other operations. In another embodiment, instructionsor sub-operations of distinct operations may be implemented in anintermittent and/or alternating manner.

Embodiments of the invention can take the form of an entirely hardwareembodiment, an entirely software embodiment, or an embodiment containingboth hardware and software elements. In one embodiment, the invention isimplemented in software, which includes but is not limited to firmware,resident software, microcode, etc.

Furthermore, embodiments of the invention can take the form of acomputer program product accessible from a computer-usable orcomputer-readable medium providing program code for use by or inconnection with a computer or any instruction execution system. For thepurposes of this description, a computer-usable or computer readablemedium can be any apparatus that can contain, store, communicate,propagate, or transport the program for use by or in connection with theinstruction execution system, apparatus, or device.

Input/output or I/O devices (including but not limited to keyboards,displays, pointing devices, etc.) can be coupled to the system eitherdirectly or through intervening I/O controllers. Additionally, networkadapters also may be coupled to the system to enable the data processingsystem to become coupled to other data processing systems or remoteprinters or storage devices through intervening private or publicnetworks. Modems, cable modems, and Ethernet cards are just a few of thecurrently available types of network adapters.

Additionally, some or all of the functionality described herein might beimplemented via one or more controllers, processors, or other computingdevices. For example, a controller might be implemented to control themooring lines, the tether(s) or tendon(s), or modes of the system.

In the above description, specific details of various embodiments areprovided. However, some embodiments may be practiced with less than allof these specific details. In other instances, certain methods,procedures, components, structures, and/or functions are described in nomore detail than to enable the various embodiments of the invention, forthe sake of brevity and clarity.

Although the operations of the method(s) herein are shown and describedin a particular order, the order of the operations of each method may bealtered so that certain operations may be performed in an inverse orderor so that certain operations may be performed, at least in part,concurrently with other operations. In another embodiment, instructionsor sub-operations of distinct operations may be implemented in anintermittent and/or alternating manner.

Although specific embodiments of the invention have been described andillustrated, the invention is not to be limited to the specific forms orarrangements of parts so described and illustrated. The scope of theinvention is to be defined by the claims appended hereto and theirequivalents.

What is claimed is:
 1. A system comprising: an unmanned underwatervehicle (UUV); a reaction structure configured to deploy from a body ofthe UUV; one or more tendons connecting the reaction structure to thebody of the UUV, wherein the reaction structure deploys at a depth belowthe body of the UUV; one or more power take-out (PTO) units coupled toor between the reaction structure and the UUV; and a control unitcoupled to the one or more PTO units to convert energy from waves on asurface of a body of water for use in other systems within the UUV. 2.The system of claim 1, wherein the control unit is further configured tostore the electrical energy.
 3. The system of claim 1, wherein the oneor more PTO units is coupled to the reaction structure.
 4. The system ofclaim 1, wherein the one or more PTO units is coupled to the UUV.
 5. Thesystem of claim 1, wherein the one or more PTO units is coupled betweenthe reaction structure and the UUV.
 6. The system of claim 1, whereinthe reaction structure is configured to move from an undeployed positionto a deployed position.
 7. The system of claim 6, wherein the undeployedposition comprises that the reaction structure is directly coupled tothe body of the UUV.
 8. The system of claim 7, wherein the deployedposition comprises that the reaction structure is only coupled to thebody of the UUV via the one or more tendons.
 9. The system of claim 1,wherein the UUV is an autonomous underwater vehicle (AUV).
 10. Thesystem of claim 1, wherein the one or more tendons have rigidconnections to the body of the UUV.
 11. A system comprising: an unmannedunderwater vehicle (UUV); a flotation structure configured to deployfrom a body of the UUV; one or more tendons connecting the flotationstructure to the body of the UUV, wherein the flotation structuredeploys above the body of the UUV; one or more power take-out (PTO)units coupled to or between the flotation structure and the UUV; and acontrol unit coupled to the one or more PTO units to convert energy fromwaves on a surface of a body of water for use in other systems withinthe UUV.
 12. The system of claim 11, wherein the control unit is furtherconfigured to store the electrical energy.
 13. The system of claim 11,wherein the one or more PTO units is coupled to the flotation structure.14. The system of claim 11, wherein the one or more PTO units is coupledto the UUV.
 15. The system of claim 11, wherein the one or more PTOunits is coupled between the flotation structure and the UUV.
 16. Thesystem of claim 11, wherein the flotation structure is configured tomove from an undeployed position to a deployed position.
 17. The systemof claim 16, wherein the undeployed position comprises that theflotation structure is directly coupled to the body of the UUV.
 18. Thesystem of claim 17, wherein the deployed position comprises that theflotation structure is only coupled to the body of the UUV via the oneor more tendons.
 19. The system of claim 11, wherein the UUV is anautonomous underwater vehicle (AUV).
 20. The system of claim 11, whereinthe one or more tendons have rigid connections to the body of the UUV.